spidev: add proper section markers

The driver already uses __devexit_p() in the structure, but looks like
actual __dev{init,exit} markings were forgotten.

The spidev_spi driver also needs renaming to include a "_driver" suffix to
avoid section mismatch warnings.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>